There are numerous components of industrial and utility equipment whose dimensional characteristics are of a critical nature and thus must be manufactured to extremely tight dimensional tolerances. Consequently, the dimensions of such components must be scrupulously inspected for quality assurance in the factory before being assembled into the equipment. A notable example of such a critical component is the flow channel of a nuclear fuel rod assembly or bundle, such as disclosed in U.S. Pat. No. 3,689,358. These channels are elongated, square, tubular components which may measure 13 centimeters on each side and on the order of 4 meters in length. It is necessary to assure that these flow channels are manufactured with their outer side surfaces sufficiently flat over their entire length so as not to obstruct the insertion of control rods between fuel assemblies in a nuclear reactor operating environment. The interior channel dimensions are also of critical concern in order to properly accept the assembly of fuel rods and spacers therein. Thus, the important dimensional characteristics of a flow channel include face or side bulge, channel width, non-square cross section at any point along its length, longitudinal bow and twist. Dimensional tolerances over the channel length may be on the order of plus/minus 0.127 mm.
Portable apparatus for measuring such dimensional characteristics of flow channels at a reactor site are disclosed in U.S. Pat. Nos. 4,197,652 and 4,274,205. An improved flow channel dimensional inspection apparatus is disclosed in the commonly assigned, copending application of Butzin, et al. entitled "Device for Dimensional Characterizing Elongated Components", Ser. No. 336,999, filed Apr. 12, 1989. While it is important to measure the dimensional characteristics of flow channels at the reactor site after they have been put into service to determine any unacceptable deviations from specification, it is equally important to determine at the factory site that these channels are manufactured strictly to specification in the first instance.